97 ECILPSE OIL PRESSURE

1997 All Other Makes All Other Models

I have a 97 spyder eclipse gs-t 2.0 automatic.

I have noticed the oil pressure is always normal when I first start the car and the engine is cold. Car runs good and shifts at appropriate times.
When 5 or 10 mins pass by of driving and my engine is at normal temperature, the Oil Pressure deacreses substantially. It does affect the cars shifting times and is noticeable.
Should I be worried? Or is this normal in older cars?